Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Linear solution keeps failing to converge

Linear solution keeps failing to converge

Linear solution keeps failing to converge

I have to parallel plates with a simple honeycomb in between (basically a sandwich structure). The bottom plat is fixed, the top one moves of a small amount in one in-plane direction. I need to see what happens to the honeycomb in shear buckling. The solution fails to converge. I reduced the time increment to 1e-07 and still I received a message it's not small enough. Shall I just keep decreasing it or is there another strategy I'm not aware of?

RE: Linear solution keeps failing to converge

Further decreasing initial time increment won’t help in this case. The error that you get is just a generoc message indicating nonconvergence. Here’s what you can try:
- check all warning messages
- make sure that all interactions (contact, tie constraints and so on) work properly and there are no rigid body motions/unconnected regions
- turn NLGEOM on if it’s off now
- use automatic stabilization in step settings
- refine the mesh and make sure that its quality is good
- consider using explicit solver

To give more detailed advice I would have to see the model. So, if you can, please attach a picture of it or, even better, share its files.

RE: Linear solution keeps failing to converge

Here the input file. when the increment is 1e-05, it aborts after 5 increment. The lower I go with the increment the more iterations I get but still not enough for convergence. I thought about moving to explicit and I think I'll go there now. Thanks!


RE: Linear solution keeps failing to converge

To solve this in Abaqus/Standard you should include imperfections (imported from eigenvalue buckling analysis). And it might be easier to run the postbuckling study using Riks method.

RE: Linear solution keeps failing to converge

Thank you for suggesting the Riks method, I was not aware of it and I will definitely look into it.

Regarding the *imperfection command: as far as I understood, I impose imperfections to my model that follow the path of buckling analysis. Is there a rule for the magnitude of the imperfections?

THank you

RE: Linear solution keeps failing to converge

When defining impoerfections you have to specify scale factor for each mode. In case of shells it is advised to use a value order of magnitude lower than the shell thickness for the first mode and decrease the factor by half for each of the subsequent modes.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


White Paper - PLM and ERP: Their Respective Roles in Modern Manufacturing
Leading manufacturers are aligning their people, processes, and tools from initial product ideation through to field service. They do so by providing access to product and enterprise data in the context of each person’s domain expertise. However, it can be complicated and costly to unite engineering with the factory and supply chain. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close